1. Field of the Invention
The invention is related to electric windshield wipers for automotive vehicles and in particular to an electric circuit which causes the windshield wiper to be intermittently actuated at predetermined intervals.
2 Description of the Prior Art
Conventional windshield wiper mechanisms for automotive vehicles when activated move a wiper blade across the vehicles' windshield in a continuing back and forth motion. When deactivated, the wiper blade is returned to a "park" position which is conventionally located at one or the other extreme position of the back and forth motion or in a concealed recess below the windshield. Under certain conditions, such as a light misty rain, or after a heavier rain, where water is splashed up on the windshield from a preceding or passing vehicle, the quantity of water on the windshield is insufficient for the wiper blade to clean the windshield properly. This often results in a smearing of dirty water, and is often accompanied by an annoying squeaking sound as the blade is moved across a relatively dry window.
To avoid this problem, the prior art has developed mechanisms which when actuated cause the wiper blade to wipe the windshield with a single back and forth motion at predetermined intervals with a dwell period between wiping cycles. Preferably, the wiper blade is returned to the park position during the dwell period.
Various types of intermittent mechanisms are known. Some of these systems, such as the windshield wiper control taught by Inoue in U.S. Pat. No. 3,649,898 use a moisture detector which activates the wiper mechanism when water is detected on the windshield. Another type, such as that taught by Tann in U.S. Pat. No. 3,643,145, uses a thermistor heated by the wiper motor current to produce a variable delay inversely proportional to amount of water on the windshield. Other types of mechanisms use blocking oscillators as taught by Foreman in U.S. Pat. No. 3,219,901 or R.C. timing circuits as taught by Rouvre in U.S. Pat. No. 3,569,812.
Collectively, the patents cited above as well as the intermittent windshield wiper mechanism presently being supplied by the automobile manufactures are dedicated systems, and can only be used with particular types of wiper mechanisms. As is known, however, almost every automotive manufacture has developed its own windshield wiper mechanism. Therefore, the intermittent system developed for the wiper mechanism of one manufacture normally cannot be used with the wiper mechanism of another manufacture without extensive modification and vice versa. The owner of a vehicle, wishing to install an intermittent wiper system or have an intermittent wiper system installed is required to return to the original manufacture of the vehicle. This limits the owner's option as to where he can purchase an intermittent wiper system and the price he will have to pay for the installation.
The invention is an intermittent wiper circuit universally adaptable to the wiper mechanism of all domestic automotive manufacturers and most foreign manufacturers and which may be installed by the owner himself or any other competent mechanic such as found at a local service station.